DESCRIPTION (Applicant's Abstract): We have found that in CD4 T lymphocytes, the gene on chromosome 11 encoding interleukin-4 can be expressed in an allelically-independent fashion and that the allelic pattern of expression (mono-allelic or biallelic) can be heritably transmitted from parent to daughter cell through an epigenetic mechanism. In a separate study, we have identified dice (determinant of IL-4 commitment), a quantitative trait locus on mouse chromosome 16, implicated in determining the proportion of recently activated CD4 T-cells that commit to IL-4 production. We have speculated that independent allelic regulation of the IL-4 gene may be a byproduct of a mechanism evolved to impart an element of probability to its expression. This proposal has three aims united by the long-term goal of understanding the biological function of allelically-independent and epigenetically heritable cytokine gene expression and to discover the molecular mechanisms responsible for this process. First, we will identify trans and cis genetic determinants of independent allelic activation of the IL-4 locus by addressing the following hypotheses: la) The probability a given IL-4 allele will be activated is genetically determined. 1b) dice is a trans determinant of the probability of IL-4 allelic activation. 2) The probability of IL-4 allelic activation is influenced by genetic elements that act in cis. 3) The probability of allelic activation at the IL-4 locus influences the probability of allelic activation at neighboring loci. Second, we will determine the structural correlates of independent allelic activation of the IL-4 locus by studying long-term antigen-specific CD4 T-cell clones to address the following hypotheses: 1) IL-4 allelic activation correlates with the appearance of allele-specific DNAse I hypersensitive sites. 2) IL-4 allelic activation correlates with allele-specific demethylation. Finally, we will resolve the genetic interval on mouse chromosome 16 that contains dice to approximately 0.2 cM to lay the groundwork for and establish the feasibility of cloning dice by position and functional rescue.